Neurobiologists believe that the neurons in the adult brain and spinal cord are impossible to rebuild once they are damaged. Thus, science provided little hope to patients suffering from brain and spinal cord injury or from neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease, among a number of others. Parkinson's and Alzheimer's diseases are examples of neurodegenerative diseases which are thought to be untreatable.
Parkinson's disease (PD), is a disorder of middle or late life, with very gradual progression and a prolonged course. HARRISON'S PRINCIPLES OF INTERNAL MEDICINE, Vol. 2, 23d ed., Ed by Isselbacher, Braunwald, Wilson, Martin, Fauci and Kasper, McGraw-Hill Inc., New York City, 1994, pg. 2275. The most regularly observed changes in patients with Parkinson's disease have been in the aggregates of melanin-containing nerve cells in the brainstem (substantia nigra, locus 20 coeruleus), where there are varying degrees of nerve cell loss with reactive gliosis (most pronounced in the substantia nigra) along with distinctive eosinophilic intracytoplasmic inclusions. (Id. at 2276). In its fully developed form, PD is easily recognized in patients, where stooped posture, stiffness and slowness of movement, fixity of facial expression, rhythmic tremor of the limbs, which subsides on active willed movement or complete relaxation, are common features. Generally, accompanying the other characteristics of the fully developed disorder is the festinating gait, whereby the patient, progresses or walks with quick shuffling steps at an accelerating pace as if to catch up with the body's center of gravity. (ld. at 2276).
The treatment of Parkinson's disease pharmacologically with levodopa combined with stereotactic surgery has only represented a partial cure, at best. (Id. at 2277). Underlying much of the treatment difficulty is directed to the fact that none of these therapeutic measures has an effect on the underlying disease process, which consists of neuronal degeneration. Ultimately, a point seems to be reached where pharmacology can no longer compensate for the loss of basal ganglia dopamine. (Id.).
Alzheimer's Disease (AD) is caused by a degenerative process in the patient which is characterized by progressive loss of cells from the basal forebrain, cerebral cortex and other brain areas. Acetylcholine transmitting neurons and their target nerves are particularly affected. Senile plaques and neurofibrillary tangles are present. Pick's disease has a similar clinical picture to Alzheimer's disease but a somewhat slower clinical course and circumscribed atrophy, mainly affecting the frontal and temporal lobes. One animal model for Alzheimer's disease and other dementias displays hereditary tendency toward the formation of such plaques. It is thought that if a drug has an effect in the model, it also may be beneficial in at least some forms of Alzheimer's and Pick's diseases. At present there are palliative treatments but no means to restore function in Alzheimer's patients.
A group of related neuronal degenerative disorders is characterized by progressive ataxia due to degeneration of the cerebellum, brainstem, spinal cord and peripheral nerves, and occasionally the basal ganglia. Many of these syndromes are hereditary; others occur sporadically. The spinocerebellar degenerations are logically placed in three groups: predominantly spinal ataxias, cerebellar ataxias and multiple-system degenerations. To date there are no treatments. Friedrich's ataxia is the prototypical spinal ataxia whose inheritance is autosomal recessive. The responsible gene has been found on Chromosome 9. Symptoms begin between ages of 5 and 15 with unsteady gait, followed by upper extremity ataxia and dysarthria. Patients are flexic and lose large-fiber sensory modalities (vibration and position sense). Two other diseases have similar symptoms: Bassen-Kornzweig syndrome (abeta-lipoproteinemia and vitamin E deficiency) and Refsom's disease (phytanic acid storage disease). Cerebellar cortical degenerations generally occur between ages 30 and 50. Clinically only signs of cerebellar dysfunction can be detected, with pathologic changes restricted to the cerebellum and occasionally the inferior olives. Inherited and sporadic cases have been reported. Similar degeneration may also be associated with chronic alcoholism. In multiple-system degenerations, ataxia occurs in young to middle adult life in varying combinations with spasticity and extrapyramidal, sensory, lower motor neuron and autonomic dysfunction. In some families, there may also be optic atrophy, retinitis pigmentosa, ophthalmoplegia and dementia.
Another form of cerebellar degeneration is paraneoplastic cerebellar degeneration that occurs with certain cancers, such as oat cell lung cancer, breast cancer and ovarian cancer. In some cases, the ataxia may precede the discovery of the cancer by weeks to years. Purkinje cells are permanently lost, resulting in ataxia. Even if the patient is permanently cured of the cancer, their ability to function may be profoundly disabled by the loss of Purkinje cells. There is no specific treatment.
Strokes also result in neuronal degeneration and loss of functional synapses. Currently there is no repair, and only palliation and rehabilitation are undertaken.
Neurotransplantation has been used to explore the development of the central nervous system and for repair of diseased tissue in conditions such as Parkinson's and other neurodegenerative diseases. The experimental replacement of neurons by direct grafting of fetal tissue into the brain has been accomplished in small numbers of patients in several research universities (including the University of South Florida); but so far, the experimental grafting of human fetal neurons has been limited by scarcity of appropriate tissue sources, logistic problems, legal and ethical constraints, and poor survival of grafted neurons in the human host brain. One method replaces neurons by using bone marrow stromal cells as stem cells for non-hematopoietic tissues. Marrow stromal cells can be isolated from other cells in marrow by their tendency to adhere to tissue culture plastic. The cells have many of the characteristics of stem cells for tissues that can roughly be defined: as mesenchyrnal, because they can be differentiated in culture into osteoblasts, chondrocytes, adipocytes, and even myoblasts. This population of bone marrow cells (BMSC) have also been used to prepare dendritic cells, (K. Inaba, et al., J Experimental Med. 176: 1693–1702 (1992)) which, as the name implies, have a morphology which might be confused for neurons. Dendritic cells comprise a system of antigen-presenting cells involved in the initiation of T cell responses. The specific growth factor, which stimulates production of dendritic cells, has been reported to be granulocyte/macrophage colony-stimulating factor 30 (GM-CSF). K. Inaba, et al., J Experimental Med. 176: 1693–1702 (1992).
Work has recently been performed using stem cells obtained from bone marrow to provide neural cells which can be used in neuronal transplantation. See WO 99/56759. This patent represented the culmination of more than 130 years of work in the use of bone marrow stem cells for non-hematopoietic uses.
Several groups of investigators since 1990 have attempted to prepare more homogenous populations of stem cells from bone marrow. For example, U.S. Pat. No. 5,087,570, issued Feb. 11, 1992, discloses how to isolate homogeneous mammalian hematopoietic stem cell compositions. Concentrated hematopoietic stem cell compositions are substantially free of differentiated or dedicated hematopoietic cells. The desired cells are obtained by subtraction of other cells having particular markers. The resulting composition may be used to provide for individual or groups of hematopoietic lineages, to reconstitute stem cells of the host, and to identify an assay for a wide variety of hernatopoietic growth factors.
U.S. Pat. No. 5,633,426 issued May 27, 1997, is another example of the differentiation and production of hematopoietic cells. Chimeric immunocompromised mice are given human bone marrow of at least 4 weeks from the time of implantation. The bone marrow assumed the normal population of bone marrow except for erythrocytes. These mice with human bone marrow may be used to study the effect of various agents on the proliferation and differentiation of human hematopoietic cells.
U.S. Pat. No. 5,665,557, issued Sep. 9, 1997, relates to methods of obtaining concentrated hematopoietic stem cells by separating out an enriched fraction of cells expressing the marker CDw 109. Methods of obtaining compositions enriched in hematopoietic megakaryocyte progenitor cells are also provided. Compositions enriched for stem cells and populations of cells obtained therefrom are also provided by the invention. Methods of use of the cells are also included.
U.S. Pat. No. 5,453,505 issued on Jun. 5, 1995, is yet another method of differentiation. Primordial tissue is introduced into immunodeficient hosts, where the primordial tissue develops and differentiates. The chimeric host allows for investigation of the processes and development of the xenogeneic tissue, testing for the effects of various agents on the growth and differentiation of the tissue, as well as identification of agents involved with the growth and differentiation.
U.S. Pat. No. 5,753,505 issued May 19, 1998, provides an isolated cellular composition comprising greater than about 90% mammalian, non-tumor-derived, neuronal progenitor cells which express a neuron-specific marker and which can give rise to progeny which can differentiate into neuronal cells. Also provided are methods of treating neuronal disorders utilizing this cellular composition.
U.S. Pat. No. 5,759,793 issued Aug. 6, 1996, provides a method for both the positive and negative selection of at least one mammalian cell population from a mixture of cell populations utilizing a magnetically stabilized fluidized bed. One application of this method is the separation and purification of hematopoietic cells. Target cell populations include human stem cells.
U.S. Pat. No. 5,789,148 issued Aug. 4, 1998, discloses a kit, composition and method for cell separation. The kit includes a centrifugable container and an organosilanized silica particle-based cell separation suspension suitable for density gradient separation, containing a polylactam and sterilized by treatment with ionizing radiation. The composition includes a silanized silica particle-based suspension for cell separation which contains at least 0.05% of a polylactam, and preferably treated by ionizing radiation. Also disclosed is a method of isolating rare blood cells from a blood cell mixture.
Within the past several years, mesenchymal stem cells (MSCs) have been explored as vehicles for both cell therapy and gene therapy. The cells are relatively easy to isolate from the small aspirates of bone marrow that can be obtained under local anesthesia: they are also relatively easy to expand in culture and to transfect with exogenous genes. Prockop, D. J. Science 26: 71–74 (1997). Therefore, MSCs appear to have several advantages over hematopoietic stem cells (HMCs) for use in gene therapy. The isolation of adequate numbers of HSCs requires large volumes of marrow (I liter or more), and the cells are difficult to expand in culture. (Prockop, io D. J. (ibid.)).
There are several sources for bone marrow tissue, including the patient's own bone marrow, that of blood relatives or others with MHC matches and bone marrow banks. There are several patents that encompass this source. U.S. Pat. No. 5,476,997 issued May 17, 1994, discloses a method of producing human bone marrow equivalent. A human hematopoietic system is provided in an immunocompromised mammalian host, where the hematopoietic system is functional for extended periods of time. In this method, human fetal liver tissue and human fetal thymus are introduced into a young immunocompromised mouse at a site supplied with a vascular system, whereby the fetal tissue results in formation of functional human bone marrow tissue.
Human fetal tissue also represents a source of implantable neurons, but its use is quite controversial. U.S. Pat. No. 5,690,927 issued Nov. 25, 1997, also utilizes human fetal tissue. Human fetal neuro-derived cell lines are implanted into host tissues. The methods allow for treatment of a variety of neurological disorders and other diseases.
U.S. Pat. No. 5,753,491, issued May 19, 1998, discloses methods for treating a host by implanting genetically unrelated cells in the host. More particularly, the present invention provides human fetal neuro-derived cell lines, and methods of treating a host by implantation of these immortalized human fetal neuro-derived cells into the host. One source is the mouse, which is included in the U.S. Pat. No. 5,580,777 issued Dec. 3, 1996. This patent features a method for the in vitro production of lines of immortalized neural precursor cells, including cell lines having neuronal and/or glial cell characteristics, comprises the step of infecting neuroepithelium or neural crest cells with a retroviral vector carrying a member of the myc family of oncogenes.
U.S. Pat. No. 5,753,506 issued May 19, 1998, reveals an in vitro procedure by which a homogeneous population of multipotential precursor cells from mammalian embryonic neuroepithelium (CNS stem cells) is expanded up to 10 fold in culture while maintaining their multipotential capacity to differentiate into neurons, oligodendrocytes, and astrocytes. Chemical conditions are presented for expanding a large number of neurons from the stem cells. In addition, four factors-PDGF, CNTF, LIF, and T3-have been identified which, individually, generate significantly higher proportions of neurons, astrocytes, or oligodendrocytes. These procedures are intended to permit a large-scale preparation of the mammalian CNS stem cells, neurons, astrocytes, and oligodendrocytes. These cells are proposed as an important tool for many cell- and gene-based therapies for neurological disorders. Another source of stem cells is that of primate embryonic stem cells. U.S. Pat. No. 5,843,780 issued Dec. 1, 1998, utilizes these stem cells. A purified preparation of stem cells is disclosed. This preparation is characterized by the following cell surface markers: SSEA-I (−); SSEA-3 (+); TRA-1-60 (+); TRA-1-81 (+); and alkaline phosphatase (+). In one embodiment, the cells of the preparation have normal karyotypes and continue to proliferate in an undifferentiated state after continuous culture for eleven months. The embryonic stem cells lines are also described as retaining the ability to form trophoblasts and to differentiate into tissues derived from all three embryonic germ layers (endoderm, mesoderm and ectoderm). A method for isolating a primate embryonic stem cell line is also disclosed in the patent.
There is substantial evidence in both animal models and human patients that neural transplantation is a scientifically feasible and clinically promising approach to the treatment of neurodegenerative diseases and stroke as well as for repair of traumatic injuries to brain and spinal cord. Nevertheless, alternative cell sources and novel strategies for differentiation are needed to circumvent the numerous ethical and technical constraints that now limit the widespread use of neural transplantation. In short, there is a need for further development of readily available reliable sources of neural cells for transplantation.
The use of umbilical cord blood for use in hematopoietic reconsitution has been around since the work of Ende in the early 1970's. Because umbilical cord blood is rich in hematopoietic precursors, including stem cells, it represents a good source of cells for hematopoietic reconstitution. To date, however, little work has been done on using pluripotential stem cells or related neural precursors which are found in umbilical cord blood for neuronal transplantion perhaps because of the failure to realize the viable source of neuronal precursors which can be found in umbilical cord blood.
Human cord and placental blood provides a rich source of hematopoietic stem cells. On the basis of this finding, umbilical cord blood stem cells have been used to reconstitute hematopoiesis in children with malignant and nonmalignant diseases after treatment with myeloablative doses of chemoradiotherapy. Sirchia and Rebulla, 1999 Haematologica 84:738–47. Early results show that a single cord blood sample provides enough hematopoietic stem cells to provide short- and long-term engraftment, and that the incidence and severity of graft-versus-host disease has been low even in HLA-mismatched transplants. These results, together with our previous discovery that bone marrow cells contain stem cells capable of differentiating into neurons and glia, led to the present invention which uses cord blood or mononuclear cell fractions thereof to repair neuronal damage in brain and spinal cord. Sanchez-Ramos, et al. 1998. Movement Disorders 13(s2): 122 and Sanchez-Ramos, et al., (2000) Exp. Neurol. 